The Jackson Laboratory (TJL) requests funding for continuation of its postdoctoral research training program in developmental genetics. Twelve members of the TJL Research staff form an interdisciplinary pool of trainee mentors. The major research training theme are the regulation of gene expression and the role of intercellular signaling in developmental decisions in mice. Another important goal of this program is training in the use of the laboratory mouse as an experimental system for the study of human development, birth defects and disease. Support is requested for four trainees. Candidates must be recent recipients of the doctoral degree (usually but not limited to the Ph.D. with 0-3 years of previous postdoctoral training). Each trainee is sponsored by a TJL faculty member in a program tailored to the trainee's individual needs and the sponsor's interests. Trainees devoted their major effort to bench research, and also are integrated into TJL seminars, short courses, workshops, and research interest groups. All trainees are required to apply for independent funding during their first year in the program, and to regularly present their work at the TJL Interest Groups and at national or international meetings. Upon completion of training, participants will be qualified to engage in creative, independent research in developmental genetics at a university, research institution, or in the biotechnology or pharmaceutical industry. The primary training facility is TJL, a private, independent research center. TJL is an NCI Cancer Research Center, distributes 3 million genetically standardized mice annually, and has held NIH research training grants continuously since 1956. During the past five years, TJL as added a new 49,000 square foot research building, 15 new members have joined the research Staff, numerous modern scientific services (e.g., Induced Mutant Resource) have been added, postdoctoral enrollment has more than doubled, and construction has begun on a new Genetics Resources Building.